This invention relates to a wobble plate piston pump adapted particularly for use as a compressor in an air conditioning system, and more particularly to means for holding the piston shoes in close proximity with the wobble plate during simultaneous swinging and rotational motion of the latter.
A variable delivery hydraulic pump has been proposed by U.S. Pat. No. 4,157,233 for instance, which comprises a drive shaft, a plurality of cylinders circumferentially arranged around the drive shaft and extending substantially parallel to the axis of same, pistons disposed to reciprocate in the cylinders, a wobble plate engaging the drive shaft for rotation in unison therewith, slipper shoes disposed in slidable contact or close proximity with the wobble plate at locations corresponding to the cylinders, and piston rods secured to the pistons and disposed in spherical engagement with the slipper shoes. According to this proposed hydraulic pump, an annular retainer member is mounted on the wobble plate in relation concentric therewith and slightly spaced from its sliding side surface. The retainer member has a plurality of through bores formed in the vicinity of its outer periphery at locations corresponding to the piston rods and loosely receiving therethrough trunk portions of the slipper shoes which in turn have their flanged portions interposed between the retainer member and the wobble plate in a manner slidable or close proximity with the latter. As the wobble plate rotates, the slipper shoes are guided along the peripheral edges of the above through bores in the retainer member to slide over or close proximity to the sliding side surface of the wobble plate. In the proposed arrangement, when the wobble plate is tilted relative to the drive shaft, a slipper shoe engaging a piston which is in its top dead center or in its vicinity is biased radially outward, and a slipper shoe engaging a piston which is in its bottom dead center or in its vicinity is biased radially inward. Thus, as the wobble plate rotates while maintaining its inclined position, the slipper shoes are radially moved relative to the center of the wobble plate so that the peripheral edges of the through bores in the retainer member are hit against the trunk portions of the slipper shoes to impede their radial movement. To prevent this, the above through bores should have a sufficiently large diameter, which, however, necessitates designing the flanged portions of the slipper shoes correspondingly large in diameter to prevent disengagement of the slipper shoes from the wobble plate through the through bores. Therefore, the conventional arrangement has the disadvantage that the slipper shoes are inevitably large in size, and the wobble plate is correspondingly large in size, resulting in a large overall size of the whole piston pump.